Improved valve econtroled spraying system

ABSTRACT

A liquid spraying system having a liquid spray section and a controller for controlling liquid to the spray section. The controller includes a valve operable between multiple positions for controlling the supply of liquid to the spray section and enabling the flow of liquid from the spray section to a flow back line only after the liquid supply to the spray section has been terminated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional PatentApplication No. 62/976,892, filed Feb. 14, 2020, which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates generally to valve controlled sprayingsystems, and more particularly, to an improved valve system forcontrolling the liquid flow to spray nozzles during operation and uponshutoff of a liquid supply.

BACKGROUND OF THE INVENTION

Agricultural sprayers typically have long spray booms with groups ofspray nozzles that are selectively controlled by respective controlvalves, each of which is individually actuated to permit transmission ortermination of liquid to the spray nozzles of the group. Termination ofliquid to one or more groups of spray nozzles frequently is necessary,for example, near the ends of fields so as to prevent spraying onnon-crop vegetation or the like. The control valves for such sprayingsystems commonly are mounted in ganged or manifolded side-by-siderelationship with respect to each other and remote from the spraynozzles they control. Each control valve is provided with a valveelement that is movable between open and closed positions to selectivelycontrol the flow of liquid to the spray nozzles of the respective group.

Control valves are known which includes a rotatable ball valve that isrotatable between a one position that enables the direction ofpressurized liquid through the control valve to the liquid supply lineto the spray nozzle or groups of spray nozzles and a second positionwhich closes a liquid inlet port of the valve and redirects remainingdownstream liquid in the line to a return line for recirculation to aliquid supply tank. During rotary movement of the ball valve to a closedposition, however, the liquid inlet port does not completely close priorto opening of a port to the return line, which results in spurts of highpressure liquid through the control valve prior to complete closure ofthe inlet port. In sophisticated agricultural sprayers today, liquiddirected in the field often is monitored by means of the quantity liquiddirected to the spray nozzles, and the redirection of liquid to thereturn line prior to valve shutoff can affect accuracy in monitoring theliquid chemical usage. While proposals have been made for preventingsuch occurrence, such proposals have been relatively complex andexpensive, requiring multiple valving mechanisms.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object to provide a valve controlled spraying system whichenables more efficient and accurate monitoring of liquid supplied to thesprayer based upon the liquid inlet feed.

Another object of the present invention to provide a valve controlledspraying system as characterized above that is operable for shutting offthe liquid supply to the spray nozzles without unwanted bursts of liquidthrough the control valve that can affect the accurate monitoring ofchemical usage.

A further object is to provide a valve controlled spraying system of theabove kind having a liquid supply control valve operable for completelyshutting of liquid supply to the spray nozzles prior to enabling thedirection of downstream liquid in spray nozzle feed lines to a returnline to the liquid supply.

Another object is to provide a valve controlled system of the above kindwhich is relatively simple in construction and operation and lendsitself to economical manufacture and reliable usage.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative spraying system havingcontrol valves in accordance with the present invention;

FIG. 2 is an enlarged fragmentary section of one of the spray nozzleassemblies and its associated check valve included in the sprayingsystem shown in FIG. 1 , showing the check valve in a closed position;

FIG. 3 is an enlarged fragmentary section of the illustrated checkvalve, showing the check valve in an open position;

FIG. 4 is an enlarged vertical section of one of the illustrated controlmodules taken in a plane perpendicular to a central liquid port of thecontrol module showing the valve stem thereof in an open position forcommunicating liquid from the central liquid supply port to an outletport of the control valve;

FIG. 5 is a vertical section, similar to FIG. 4 , but showing the valvestem in a lowered position which blocks the flow of liquid from theliquid supply port to an outlet port to the spray nozzles while openinga flowback or return port communicating with a return line;

FIG. 6 is a vertical section of the control module shown in FIG. 5 takenin a plane perpendicular to that of FIG. 5 ;

FIG. 7 is a partial section of the control module, similar to FIG. 4 ,showing the valve stem in an open position permitting communication ofliquid through an outlet port to spray nozzles;

FIG. 8 is a figure similar to FIG. 7 , but showing the valve stem in anintermediate position blocking the flow of liquid to both the liquidoutlet port to the spray nozzles and to the flowback or return port ofthe module;

FIG. 9 is a partial section similar to FIGS. 5 and 6 , showing the valvestem in a lowered position blocking the flow of liquid through the inletport and permitting the return flow of liquid to a flowback or returnport;

FIG. 9A is an enlarged blow up of the lower valve stem in FIG. 9 ;

FIG. 10 is an enlarged perspective of the electric motor and valve stemdrive of the illustrated control module;

FIG. 11 is an enlarged horizontal section of the control module taken inthe plane of line 11-11 in FIG. 7 ;

FIG. 12 is a side elevational view of the electric motor and valve stemdrive of the illustrated control module; and

FIG. 13 is a section of the motor and valve stem drive taken in theplane of line 13-13 in FIG. 12 .

While the invention is susceptible to various modifications andalternative constructions, a certain illustrated embodiment thereof hasbeen shown in the drawings and will be described in detail below. Itshould be understood, however, that there is no intention to limit thepresent invention to the disclosed structural form. On the contrary, theintention is to cover all modifications, alternative constructions, andequivalents that fall within the spirit and scope of the invention.Hence, while the present invention will be described in connection withgang mounted control valves for an agricultural spraying system, it willbe understood that the invention is equally applicable to control valvesfor other types of liquid spraying or transfer systems.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now more particularly to FIG. 1 of the drawings, there isshown an illustrative agricultural spraying system 10 which includes asupply tank 11 for containing a quantity of liquid to be sprayed, aplurality of spray sections 12 each having a plurality of spray nozzles14 through which liquid is discharged, and a group of spray controlvalves 15 in accordance with the invention which are mounted in a gangedor manifolded side-by-side relationship with respect to each other andare adapted to control the flow of liquid from the supply tank 11 to thespray sections 12. Basically, the spraying system 10 is similar to thatdisclosed in the above referenced U.S. Pat. No. 6,036,107, thedisclosure of which is incorporated herein by reference.

As is customary in agricultural sprayers, the spraying system 10includes a supply line 18 between the supply tank 11 and the group ofcontrol valves 15 for transmitting liquid to the control valves 15, adischarge line 19 between each control valve 15 and a respective spraysection 12 for delivering liquid to the spray section 12, a return line20 that provides return communication between the control valves 15 andthe supply tank 11, and a regulation line 21 having a regulation valve22 between the group of control valves 15 and the supply tank 11 forfacilitating regulation of the system pressure.

The supply line 18 of the illustrated spraying system 10 includes ashut-off valve 24 which permits manual flow stoppage of liquid from thesupply tank 11, a pump 25 which pressurizes liquid in the supply line18, a strainer 26 for filtering debris from the supply line 18, and athrottling valve 28 which permits manual regulation of flow. The supplyline 18 also includes a return line 29 which, in this case, branches offfrom the supply line 18 at a point downstream of the pump 25 and returnsto the supply tank 11. As shown in FIG. 1 , this return line 29 includesan agitator 30 located within the supply tank 11 which mixes the liquidwithin the supply tank 11 based upon the flow rate through the returnline 29. A throttling valve 31 also is provided in the return line 29which may be manually adjusted to regulate the flow rate through thereturn line 20 and to adjust the mixing rate of the agitator 30. Theillustrated spraying system 10 is provided with a computer operatedsprayer control 35 which is operatively connected to each of the controlvalves 15 of the group and the regulating valve 22, in a known manner.

The illustrated spray nozzles 14, as depicted in FIGS. 2 and 3 , may beof conventional type, in this case each having a nozzle body 38 with astem 39 supported in fluid communication with a liquid supply boom 40 ofthe spray section 12, which in turn is coupled to a respective supplyline 19. The spray nozzles 14 each have a have a respective check valve41, such as disclosed in commonly assigned U.S. Pat. No. 4,660,598, thedisclosure of which is incorporated herein by reference. When thepressure of liquid delivered to the spray nozzle 14 via the supply line19 exceeds the force of a biasing spring 42, the pressurized liquidurges a diaphragm 45 away from an upstream end 46 of an inlet tube 48 asshown in FIG. 3 , so as to enable liquid to flow through the inlet tube48 and be discharged from the spray nozzle. Upon shutting off ofpressurized liquid from the supply source, the spring 42 forces thediaphragm into sealing engagement with the upstream end of the tube 48so as to prevent further liquid from discharging or dripping from thespray nozzle 14.

The control valves 15 of the spray sections 12 each have a modularconstruction and are mounted in ganged or manifold relation in a mannersimilar to that disclosed in the above referenced U.S. Pat. No.6,036,107. The control valves 15, as shown in FIGS. 4-6 each have a mainvalve body 50, a lower valve body 51 supported in depending relation tothe main valve body 50, and an electric valve control motor 52 supportedon top of the main valve body 50. The main valve body 50 in this casehas an upwardly opening annular collar 54 that receives and supports anannular mounting section 55 of a housing of the motor 52 with an annularsealing rings 56 there in between, and the lower valve body 51 has anupwardly extending reduced diameter hub section 58 supported within alower end of the main valve body 50 with sealing O-ring 59 therebetween.The main valve body 50 includes a central transversely oriented mainliquid supply port 60 for receiving liquid from the supply line 18, andthe lower valve body 51 has a central vertical liquid passage 62 forcommunication with the liquid supply port 60. The central verticalpassage 62 in turn communicates with a transverse passage 64 having aliquid outlet port 65 and a reduced downstream flowback or return port66 adjacent a lower end of the valve body 51. The control valves 15 areganged with the liquid supply ports 60 of the plurality of controlvalves communicating with each other and with the liquid supply line 18,and with each liquid outlet port 65 being coupled to a respective liquidsupply line 19 to a spray section 12 and each liquid flowback or returnport 66 coupled to the return line 20.

In accordance with an important feature of the present embodiment, eachcontrol valve 15 has a single valve stem 70 for controlling the flow ofliquid from the main liquid supply port 60 to the outlet port 65 andrespective supply line 19 and to the liquid flowback or return port 66and return line 20. To this end, the valve stem 70 extends centrallythrough the main valve body 50, the liquid supply port 60, and thecentral liquid supply passage 62 of the lower valve body 51. The valvestem 70 in this case extends the length of the main and lower valvebodies 50, 51 with a lower end thereof being positionable through alower flowback or return port 66. An annular seal 71 is supported abouta lower end of the valve stem 70 (FIG. 9A) for sealing contact with thereduced diameter flowback or return port 66, as will become apparent.For ease of manufacture, the valve stem 70 in this case has an upper andlower sections 70 a, 70 b fixedly secured together by a threadedcoupling 72.

For controlling the supply of liquid from the liquid supply port 60 tothe central passage section 62 and outlet port 65 of each spray nozzle14, an annular seal 75 is supported on the stem 70 within the mainliquid supply port 60, as depicted in FIG. 4 . The main annular seal 75is biased downwardly against an E-clip 76 fixed to the stem 70 by a coilspring 78 interposed between a washer 79 on an upper side of the annularseal 75 and an upper E-clip 80 fixed to the stem a distance above thewasher 79. An O-ring seal 81 in this case is mounted in surroundingrelation to the valve stem 70 within the annular seal 75.

For raising and lowering the valve stem 70 between open and closedpositions, the electric motor 52 is operatively coupled to the valvestem 70. To this end, the electric motor 52 may be a 12 V DC, reversiblemotor, having a drive shaft 85 coupled to a drive train 86 for rotatingan output shaft 88 supported in depending relation to the drive train 86above valve steam 70. To facilitate controlled raising and lowering thevalve stem 70 as an incident to rotation of the output shaft 88, anoptical switch flag 89 affixed to an upper end of the valve stem 70 isthreadedly supported on a threaded section 90 the output shaft 88. Theswitch flag 89 is retained against rotation such that driven rotation ofthe output shaft 88 will cause that switch flag 89 and valve stem 70coupled to the underside thereof to be raised or lowered relative to thevalve bodies 50, 51. For guiding raising lowering of the switch flag 89,and hence the valve stem 70, a transverse leg section 89 a on one sideof the flag switch 89 is guided for movement within a guide track 92fixed within the motor housing (FIG. 11 ).

For controlling upper and lower movement of the valve stem 70, theswitch flag 89 has a thinner leg section 89 b on a side opposite theguide flag section 89 a and is movable with the valve stem 70 betweenoptical sensors 95 a, 95 b that control the electric motor 52 and limitupper and lower movement of the switch flag 89, and hence the valve stem70. The optical sensors 95 a and 95 b in this case are coupled to acircuit board 96 (FIG. 10 ) that effects operation of the electric motor52, via an appropriate operator control, and movement of the valve stem70 between the sensors 95 a, 95 b.

In keeping with a further important aspect of the present embodiment,each control valve 15 is operable such that the valve stem 70 completelycloses and seals off communication between the main liquid inlet port 60and the central flow passageway 62 to the outlet port 65 to the spraysection 12 prior to enabling communication from the outlet port 65 andsupply line 19 to the flowback or return port 66. As depicted in FIGS. 4and 7 , when the electric motor 52 has rotated the output shaft 88 toraise the flag switch 89 and valve stem 70 coupled thereto to an upperposition with the flag switch section 89 b in contact with the upperoptical sensor 95 a, the annular seal 75 carried by the valve stem 70 israised to an open position permitting communication of liquid from themain inlet port 60 of the control module to the central and transversepassage sections 62, 65 and output port 65 to the spray system 12. Thelower E-clip 76 carries and supports the annular seal 75 to such raisedor open position. Simultaneously, the lower end of the valve stem 70 israised and positioned in a closed position in the flowback or returnport 66, with the annular seal 71 preventing passage of liquid from boththe central passage 62 and outlet port 60 to the flowback or return port66.

For preventing liquid communication to the outlet port 65 and spraysection 12, the electric motor 52 is operated in the reverse directionunder control for the circuit board 96, rotating the output shaft 88 inan opposite direction that lowers the optical switch flag 89 and valvestem 70 downwardly to an intermediate position that initially closesboth the liquid inlet port 60 while flowback and return port 66 remainsclosed, as depicted in FIG. 8 . In such intermediate position it can beseen that the annular seal 75 is biased into position closing the inletport 60 while the lower valve stem 70 continues to close the flowbackport 66. Continued operation of the drive motor 52 and rotation of theoutput drive shaft 88 further lowers the valve stem 70 a sufficientdistance that the annular seal 71 at the lower end of the valve stem 70is disposed beyond the reduced diameter flowback or return port 66.During such movement, the annular seal 75 remains biased by the biasingspring 78 in its closed position, while the valve stem 70 and the E-clip76 that supports the annular seal 75 continue to move downwardly withthe valve stem 70 (FIGS. 6 and 9 ). Upon lowering of the valve stem 70and optical switch flag 89 to the level that the flag section 89 bcontacts the lower optical sensor 95 b, the lower end of the valve stem70 and annular seal 65 are disposed beyond the reduced diameter outletor return port 66, thereby enabling communication of any downstreamliquid to be drained back through the flowback outlet 66 to the returnline 20. It will be appreciated that since the inlet port 60 iscompletely closed prior to opening of the flowback or return port 66,there are no bursts or any other communication of liquid from the inletport 60 to the return port 66 and return line 15 during liquid shutoffto the spray section 12 or other appreciable loss of supply liquid thatsignificantly affects reliable monitoring of the liquid chemical or thelike.

To resume spraying, the drive motor 52 can be operated in reversedirection, raising the switch flag 89 and valve stem 70 to a positionthat first closes the flowback or return port 66 while the annular seal75 remains biased in a position closing the inlet port 60 and then uponcontinued raising of the valve stem 70 and to the level that the opticalswitch flag section 89 b engages the upper optical sensor 95 a. Suchfurther movement causes the E-clip 76 to lift the annular seal 75 andopen the main liquid supply port 60, as depicted in FIG. 4 , forcommunicating liquid to spray section 12.

From the foregoing, it can be seen that a valve control spraying systemis provided that is operable for shutting off and turning on the liquidsupply to the spray nozzles without unwanted bursts of liquid throughthe control valve that can affect accurate monitoring of liquid chemicalusage. The valving system utilizes a single valve stem that iscontrolled for completely shutting off liquid to the spray nozzles priorto enabling drainage of liquid to a return line of the spraying system.It can also be seen that the valve control system is relatively simplein construction and operation and lends itself to economical manufactureand reliable usage.

1. A liquid spraying system comprising: a liquid spray section having atleast one liquid spray nozzle; a liquid controller for controlling theflow of liquid from a liquid supply to said spray section for dischargefrom said at least one spray nozzle; said liquid controller including aliquid control valve having a valve body with a liquid supply port and aliquid flow back port; a first liquid supply line for directing liquidfrom said liquid supply to said liquid supply port; a second liquidsupply line for directing liquid from said liquid supply port to saidspray section; a flow back line coupled to said flow back port fordirecting liquid in said second liquid supply line away from said spraysection upon termination of the supply of liquid to said spray section;said control valve having a valve stem; said control valve beingoperable for moving said valve stem between (1) a first position thatopens said liquid supply port for enabling the direction of liquid fromsaid first liquid supply line through said liquid supply port to saidsecond liquid supply line and liquid spray section for discharge from atleast one spray nozzle while blocking flow of liquid through said flowback port to said flow back line, (2) a second position that blocks thesupply of liquid from first liquid supply line through said liquidsupply port to said second liquid supply line while continuing to blockthe flow of liquid through said flow back port to said flow back line;and (3) to a third position wherein during movement to said thirdposition said valve stem continues to block the flow of liquid from saidfirst liquid supply line through said liquid supply port while openingsaid flow back port for allowing remaining liquid in said second liquidsupply line to flow back through said flow back port and flow back linesuch that the flow of liquid from said second liquid supply line to saidliquid flow back line is only possible when said liquid supply port isclosed.
 2. The liquid spraying system of claim 1 in which said valvestem extends through both said liquid supply port and flow back port andin said first position allows the flow of liquid from through liquidsupply port to said second liquid supply line while simultaneouslyblocking the flow through said flow back port, and in said secondposition simultaneously blocks the flow of liquid through both saidliquid supply port and flow back port, and upon movement of said valvestem to said third position continues to block the flow of liquidthrough said supply port and then opens said the flow back port forallowing remaining liquid in said second liquid supply line to flow tosaid flow back line.
 3. A liquid spraying system of claim 1 in whichsaid valve stem is threadedly supported in said valve body for relativelongitudinal movement, and including a motor coupled to said valve stemfor selectively rotating said valve stem for moving said valve stembetween said first, second, and third positions.
 4. The liquid sprayingsystem of claim 3 including a control for controlling operation of saidmotor, said control including a switch carried by said valve stem formovement with said valve member between said first, second and thirdpositions, and a pair of longitudinally spaced sensors on said valvebody engageable by said switch for controlling operation of said motorand limiting movement of said valve stem between said first and saidthird positions.
 5. The spraying system of claim 1 in which said valvestem carries a first sealing member for closing said liquid supply portwhen said valve stem is in said second and third positions and a secondsealing member for closing said flow back port when said valve stem isin said first and second positions.
 6. The spraying system of claim 5 inwhich said first sealing member is an annular sealing member mounted onsaid valve member and spring biased for relative movement such that uponmovement of said valve stem from said first position to said second andthird positions said first sealing member closes said liquid supply portwhile allowing continued movement of said valve stem to said second andthird positions.
 7. The spraying system of claim 1 in which said valvebody has an elongated liquid flow passage communicating between saidliquid supply port and said flow back port; said valve stem beingmounted for reciprocating movement in said elongated flow passagebetween said first, second and third positions; said second liquidsupply line communicating with said elongated liquid passage at anintermediate location between said liquid supply port and flow backport; and said valve stem when in said first 1 permits the flow ofliquid from said liquid supply port through said elongated liquid flowpassage to said second liquid supply line while blocking the flow ofliquid through said flow back port to said flow back line, and when insaid second position blocks the flow of liquid through said liquidsupply port to said elongated liquid flow passage while simultaneouslyblocking the flow of liquid from said elongated flow passage throughsaid flow back port, and as an incident to movement to said thirdposition opens said flow back port for enabling communication of liquidfrom said second liquid supply line and through said elongated passageand flow back port to said flow back line and while continuing to blockthe flow of liquid from said liquid supply through said liquid supplyport to said elongated passage.
 8. A liquid spraying system comprising:a liquid spray section having at least one liquid spray nozzle; a liquidcontroller for controlling the flow of liquid from a liquid supply tosaid spray section for discharge from said at least one spray nozzle;said liquid controller including a liquid control valve having a valvebody with a liquid supply port, a liquid outlet port, and a liquid flowback port; a first liquid supply line for directing liquid from saidliquid supply to said liquid supply port; a second liquid supply linefor directing liquid from said liquid outlet port to said spray section;a flow back line coupled to said flow back port for directing liquid insaid second liquid supply line away from said spray section upontermination of the supply of liquid to said spray section; said controlvalve having a valve stem; said central valve being operable for movingsaid valve stem between (1) a first position that opens said liquidsupply port for enabling the direction of liquid from said first liquidsupply line through said liquid supply port and liquid outlet port tosaid second liquid supply line and liquid spray section for dischargefrom at least one spray nozzle while blocking flow of liquid throughsaid flow back port to said flow back line, (2) a second position thatblocks the flow of liquid from said first liquid supply line throughsaid liquid supply port and outlet port to said second liquid supplyline while simultaneously blocking the flow of liquid through said flowback port to said flow back line; and (3) to a third position whereinduring movement to said third position said valve member continues toblock the flow of liquid from said first liquid supply line through saidliquid supply port and outlet port while opening said flow back port forallowing remaining liquid in said second liquid supply line to flow backthrough said flow back port and flow back line such that the flow ofliquid from said second liquid supply line to said liquid flow back lineis only possible when said liquid supply port is closed.
 9. The liquidspraying system of claim 8 in which said valve body has a liquid flowpassage communicating between said liquid supply port and said flow backport; and said second liquid supply line communicates with said valvebody liquid flow passage at a location between said liquid supply portand liquid flow back port.
 10. The liquid spraying system of claim 9 inwhich said valve stem extends through said valve body liquid flowpassage and both said liquid supply port and flow back port and in saidfirst position allows the flow of liquid from through liquid supply portto liquid outlet port and second liquid supply line while simultaneouslyblocking the flow through said flow back port, and in said secondposition simultaneously blocks the flow of liquid through both saidliquid supply port and flow back port, and upon movement of said valvestem to said third position continues to block the flow of liquidthrough said supply port and then opens said the flow back port forallowing remaining liquid in said second liquid supply line to flow tosaid flow back line.
 11. A liquid spraying system of claim 9 in whichsaid valve stem is threadedly supported in said valve body for relativelongitudinal movement, and including a motor coupled to said valve stemfor selectively rotating said valve stem for moving said valve stembetween said first, second, and third positions.
 12. The spraying systemof claim 9 in which said valve stem carries a first sealing member forclosing said liquid supply port when said valve stem is in said secondand third positions and a second sealing member for closing said flowback port when said valve stem is in said first and second positions.13. The spraying system of claim 12 in which said first sealing memberis mounted on said valve stem and spring biased for relative movementsuch that upon movement of said valve stem from said first position tosaid second position said first sealing member closes said liquid supplyport while allowing continued movement of said valve stem to said secondand third positions.
 14. The spraying system of claim 13 in which saidvalve stem carries a second annular sealing member in longitudinallyspaced relation to said first sealing member that blocks the flow ofliquid through said flow back port to said flow back line when saidvalve stem is in said first and second positions and upon movement ofsaid valve stem to said third position is carried by the valve stem to aposition that opens said flow back port for permitting the flow ofliquid from said second liquid supply line through liquid outlet portand flow back port to said flow back line.
 15. A liquid spraying systemcomprising: a spray boom defining a liquid flow passage and supporting aplurality of spray nozzles which each have a discharge orifice in fluidcommunication with the liquid flow passage; a control valve forcontrolling the flow of liquid from a liquid supply to said spray boomliquid flow passage; said control valve having a valve body with aliquid supply port and a liquid flow back port; a first liquid supplyline coupled to said supply port for directing liquid from said liquidsupply to said liquid supply port; a second liquid supply line fordirecting liquid from said liquid supply port to said spray boom liquidflow passage; and a flow back line coupled to said flow back port fordirecting liquid in said second liquid supply line away from said sprayboom upon termination of the supply of liquid to said spray boom; saidcontrol valve having a valve member selectively moveable between (1) afirst position that opens said liquid supply port for enabling thedirection of liquid from said first liquid supply line through saidliquid supply port to said second liquid supply line and liquid spraysection for discharge from said plurality of spray nozzle while blockingflow of liquid through said flow back port to said flow back line, (2) asecond position that blocks the supply of liquid from first liquidsupply line through said liquid supply port to said second liquid supplyline while continuing to block the flow of liquid through said flow backport to said flow back line; and (3) to a third position wherein duringmovement to said third position said valve member continues to block theflow of liquid from said first liquid supply line through said liquidsupply port while opening said flow back port for allowing remainingliquid in said second liquid supply line to flow back through said flowback port to said flow back line such that the flow of liquid from saidsecond liquid supply line to said liquid flow back line is only possiblewhen said liquid supply port is closed.
 16. The liquid spraying systemof claim 15 in which said valve body has a liquid flow passagecommunicating between said liquid supply port and said flow back port;and said second liquid supply line communicates with said valve bodyliquid flow passage at a location between said liquid supply port andliquid flow back port.
 17. The liquid spraying system of claim 1 inwhich said valve member is an elongated valve stem that extends throughboth said liquid supply port and flow back port and in said firstposition allows the flow of liquid from through liquid supply port tosaid second liquid supply line while simultaneously blocking the flowthrough said flow back port, and in said second position simultaneouslyblocks the flow of liquid through both said liquid supply port and flowback port, and upon movement of said valve stem to said third positioncontinues to block the flow of liquid through said supply port and thenopens said the flow back port for allowing remaining liquid in saidsecond liquid supply line to flow to said flow back line.
 18. A liquidspraying system of claim 17 in which said valve stem is threadedlysupported in said valve body for relative longitudinal movement, andincluding a motor coupled to said valve stem for selectively rotatingsaid valve stem for moving said valve stem between said first, second,and third positions.
 19. The spraying system of claim 17 in which saidfirst sealing member is mounted on said valve stem and spring biased forrelative movement such that upon movement of said valve stem from saidfirst position to said second position said first sealing member closessaid liquid supply port while allowing continued movement of said valvestem to said second and third positions.
 20. The spraying system ofclaim 18 in which said valve stem carries a second annular sealingmember in longitudinally spaced relation to said first sealing memberthat blocks the flow of liquid through said flow back port to said flowback line when said valve stem is in said first and second positions andupon movement of said valve stem to said third position is carried bythe valve stem to a position that opens said flow back port forpermitting the flow of liquid from said second liquid supply linethrough liquid outlet port and flow back port to said flow back line.